I finally threw away my Nalgene bottles last week after clinging to them for years, despite the warnings from environmental scientists that the polycarbonate plastic bottles contained nasty chemicals called endocrine disruptors. I love my Nalgene bottles. They’re indestructible, convenient, and have probably saved me thousands of purchases of bottled water. So despite the gnawing doubts, I’ve kept on using them. But last week I read a new study that put the final nail in the coffin, at least as far as I’m concerned.

We’ve known for a long time that polycarbonate plastic contains a chemical called Bisphenol-A (BPA). BPA is the quintessential endocrine disruptor. (An endocrine disruptor is a pollutant that can mimic hormones in the human body. The pollutant can plug into the body’s hormone receptors and scramble the critical growth & development signals that hormones carry, increasing risks for all kinds of health problems, from cancer to fertility to obesity.

The argument has been over whether or not the polycarbonate plastic bottles leach BPA into drinking water under normal conditions. The evidence is pretty strong that super-heating bottles or exposing them to harsh detergents releases BPA. But what happens to drinking water under normal use conditions?

A team of researchers at the University of Cincinnati College of Medicine recently put that question to the test in a new study. They bought brand new Nalgene bottles at a camping store, and got a bunch of rock climbers at the local climbing gym to donate some used ones. They found that at room temperature, the bottles steadily leached measurable amounts of BPA into the drinking water (measurable in ng/hour). The longer the water sat in the bottles, the more BPA they could measure in the water. They even used a standard test to confirm that the levels of BPA they were measuring mimicked the toxic action of estrogen to developing cerebellar neurons. Filling the bottles with just-boiled water (as many of us are wont to do while camping) dramatically increased the migration of BPA into the water by as much as 55-fold.

Several previous studies have also looked at BPA migration from polycarbonate infant formula bottles, food and beverage containers. The upshot is that we are exposed to endocrine disruptors, including BPA, from a wide variety of sources, and each of them contributes to our total burden of exposure throughout our lives. While this particular study doesn’t say that you can pin your health problems on your water bottle, the authors strongly state that they are one component of our total exposure to endocrine disruptors. Some of these exposures you can’t really change – at least not without changing environmental regulations. But many of them can be changed – starting with pitching the polycarbonate water bottle.

PS: Need suggestions for a replacement bottle? I carry around an old Gatorade bottle that I refill with water (just avoid bottles with a #3 or #7 on the bottom). You can also find lightweight stainless steel or enameled aluminum bottles at some health food and sporting goods stores.